1. Field of the Invention
The present invention relates to combine harvesters and is concerned with the design of unloading tubes by which the grain tanks of such harvesters are unloaded.
2. Description of the Prior Art
It is known to provide combine harvesters with pivotally mounted unloading tubes which, for transport purposes, are positioned alongside the harvesters but which, for unloading the grain tanks, can be pivoted to positions generally transverse of the central vertical fore-and-aft planes of the harvesters. In the unloading position, the unloading tube is aligned with a discharge opening in the grain tank and is coupled thereto so as to be able to receive grain from the grain tank without any grain losses occurring. The unloading tube contains an unloading auger, which in the operative unloading position can be coupled to another auger in the grain tank for unloading the grain. With this arrangement unloading is only possible in one position (i.e. the unloading position) of the unloading tube.
So-called "closed" unloading tubes have been proposed to enable the grain tank to be unloaded in a series of positions of the unloading tube and to enable the discharge end of the unloading tube to be moved above a grain receiving trailer, so as to load the trailer more evenly and completely. In these arrangements the unloading tube is normally pivotally mounted on a transition tube which is disposed between the grain tank and the unloading tube and which contains coaxially therein a transition shaft, which is frequently in the form of a transition auger shaft. Complicated drive arrangements, e.g. a plurality of bevel gears, are provided to drive the unloading auger and the grain tank auger. Hence such "closed" unloading tubes are expensive.
Unloading tubes of the known type described above are disclosed in British Patent Specifications Nos. 1,086,037, 1,251,136 and 1,264,732.
Other "closed" unloading tubes (e.g. Germany OS No. 2.412.816, U.S. Pat. No. 3,938,684) have been proposed wherein the drive arrangements are of such a type that operation is only possible in one position or in only a very restricted range of positions. To avoid damage which would occur if the drive line is energized when the unloading tube is not properly positioned in its unloading position, special safety devices have to be provided. These safety devices are complicated and hence expensive.